Glass Scaffolds Designed to Repair Bones Also Show Potential as Weight-Bearing Implants

By BiotechDaily International staff writersPosted on 08 Aug 2013

Image: Researchers from Missouri University of Science and Technology have developed a type of glass implant that could one day be used to repair injured bones in the arms, legs and other areas of the body that are most subject to the stresses of weight (Photo courtesy of Missouri University of Science and Technology).

Researchers have developed a type of glass implant that could soon be used to heal damaged bones in the legs, arms, and other areas of the body that are most exposed to the weight-bearing stresses.

This is the first time researchers have shown a glass implant strong enough to bear weight can also integrate with bone and promote bone growth, according to lead researcher Dr. Mohamed N. Rahaman, professor of materials science and engineering at Missouri University of Science and Technology (S&T; Rolla, USA).

In earlier studies, the Missouri S&T researchers developed a glass implant strong enough to handle the weight and pressure of repetitive movement, such as walking or lifting. In their most recent study, published in the July 2013 issue, and available online in the journal Acta Biomaterialia, the researchers reported that in the form of a porous scaffolding, the glass implant, in addition, combines with bone and stimulates bone growth.

This fusion of strength and bone growth opens new possibilities for bone repair, according to Dr. Rahaman, who also directs Missouri S&T’s Center for Biomedical Science and Engineering, where the research was conducted. “Right now, there is no synthetic material that is practical for structural bone repair,” Dr. Rahaman said.

Traditional approaches to structural bone repair involve either the use of a porous metal, which does not reliably heal bone, or a bone allograft from a cadaver. Both approaches are costly and carry risks, according to Dr. Rahaman. He believes the type of glass implant developed in his center could provide a more feasible approach for repairing injured bones. The glass is bioactive, which means that it reacts when implanted in living tissue and convert to a bone-like material.

Dr. Rahaman and his coworkers, in their latest research, implanted bioactive glass scaffolds into sections of the calvarial bones (skullcaps) of laboratory rats, then examined how well the glass integrated with the surrounding bone and how quickly new bone grew into the scaffold. The scaffolds were created in Dr. Rahaman’s laboratory through a process known as robocasting, a computer-controlled technique to make materials from ceramic slurries, layer by layer, to ensure uniform structure for the porous material.

The Missouri S&T researchers, in previous studies with porous scaffolds of the silicate glass, known as 13-93, were found to have the same strength characteristics as cortical bone. Cortical bones are those outer bones of the body that bear the most weight and undergo the most repetitive stress. They include the long bones of the arms and legs.

However, what Dr. Rahaman and his colleagues could not determine was how well the silicate 13-93 bioactive glass scaffolds would integrate with bone or how quickly bone would grow into the scaffolding. “You can have the strongest material in the world, but it also must encourage bone growth in a reasonable amount of time,” stated Dr. Rahaman. He considers three to six months to be a reasonable time frame for completely regenerating an injured bone into one strong enough to bear weight.

In their study, the S&T researchers found that the bioactive glass scaffolds bonded quickly to bone and promoted a substantial amount of new bone growth within six weeks. Whereas the skullcap is not a load-bearing bone, it is principally a cortical bone. The aim of this research was to demonstrate how well this type of glass scaffolding, already shown to be strong, would interact with cortical bone.

Dr. Rahaman and his fellow researchers in the Center for Biomedical Science and Engineering are now studying true load-bearing bones. They are now evaluating the silicate 13-93 implants in the femurs (leg bones) of laboratory rats. In the future, Dr. Rahaman plans to experiment with modified glass scaffolds to see how well they enhance specific characteristics within bone. For instance, doping the glass with copper should promote the growth of blood vessels or capillaries within the new bone, while doping the glass with silver will give it antibacterial properties.